#include <stdio.h>

#define N 101

int main(void) {
    int i;
    double x, result = 1.0, item = 1.0;
    scanf_s("%lf", &x);
    for (i = 1; i < N; i++) {
        item *= x / i;
        result += item;
    }
    printf("%.5lf", result);
    return 0;
}
